Prevention or inhibition of muscle breakdown, and the facilitation of efficient muscle repair is of great interest to athletes, the elderly, and those with muscle-wasting conditions. A wide range of products and methods have been proposed for enhancing healthy muscle tissues and enhancing athletic performance. Existing compositions and methods which are available for these purposes suffer from a variety of shortcomings. These shortcomings range from potentially dangerous side affects, to a lack of bioavailability and difficulty in formulation and/or administration.
It is well known that proteins are converted to amino acids in the digestive system and that the resulting amino acids are used by the body for growth and development. In certain medical situations a patient may be unable to receive proteins. In these situations patients have been given free amino acids. Free amino acids, however, are sometimes not tolerated well by patients and may cause diarrhea and dehydration. Also, the free amino acids may be unstable and/or difficult to formulate.
It has been observed that the body can more effectively absorb certain small molecules called dipeptides or tripepetides. These molecules consist of, for example, two to three amino acids. It has been observed, for example, that peptides containing the amino acid residue glycine in the N-terminal position are readily assimilable. See for example, U.S. Pat. No. 4,340,592.
European Patent Application No. 0,182,356 discloses a nutritional composition containing at least one oligopeptide consisting of a dipeptide or a tripeptide wherein the N-terminal amino acid residue is selected from the class consisting of alanine, lysine and arginine.
One group conducting research in this area concluded that glycine is generally superior to other amino acids as the N-terminal amino acid residue in a dipeptide. This superiority was attributed to a greater fraction of such an intravenously administered dipeptide reaches the tissues. S. Adibi et al., Influence of Molecular Structure on Half-life and Hydrolysis of Dipeptides in Plasma: Importance of Glycine as N-Terminal Amino Acid Residue, 35 Metabolism 850, 835 (1986).
Two European patents, 0,087,751 and 0,087,750 disclose water-soluble peptides. The '751 patent discloses a method to parenterally administer low water-soluble amino acids. Two amino acids, tyrosine and cystine, individually have low solubility in water. These amino acids, however, are clinically useful and, therefore, it was desirable to find an effective formulation. The '751 patent describes an infusion method which involves bonding these relatively insoluble amino acids to the amino acid lysine to produce a tripeptide.
The '750 patent discloses the infusion of glutamine as a derivative substituted by α-aminoacyl residues on the a amino group. That is, glutamine is in the “c-terminal” position, in that its alpha amino nitrogen becomes part of the peptide bond with the other amino acid. The preferred dipeptide preparation disclosed in the '750 patent is alanyl-glutamine. The aminoacylation of glutamine is reported to achieve a stabilization of the terminal amide group.
Experiments involving the use of total parenteral nutrition (TPN) containing glycyl-glutamine dipeptides, however, suggest potential adverse effects of the TPN formulation containing glycyl-glutamine (U.S. Pat. No. 5,189,016).
Two commercially available dipeptides of glutamine are Dipeptiven, which is an alanyl-glutamine (Fresenius Laboratories, Germany) and Glamin (Pharmacia and Upjohn Laboratory, Sweden), which is an amino acid solution containing glycyl-glutamine dipeptide. To this date, there are no studies of the arginyl-L-glutamine dipeptide.
It is well known that nutrition can impact the functioning of the immune system. Proper nutrition can promote healthy immune responses. There are many aspects to the immune response of humans and animals. One component of the immune response is mucosal immunity. Mucosal immunity provides a first line of defense for the body against a broad range of pathogens.
There remains a great need in the art for compositions and methods which promote healthy muscle tissue, reduce muscle deterioration, and/or promote a healthy immune system.